Corrosion prevention



CORROSION PREVENTION Paul W. Fischer, Whittier, Califl, assignor to Union Oil Company of California, Los Angeles, Calif., 21 corporation of California No Drawing. Application October 21, 1957 Serial No. 691,178

14 Claims. (Cl. 103-44) This invention relates to methods and compositions for preventing the corrosion of ferrous metals, and in particular relates to novel corrosion inhibiting compositions having lubricating characteristics.

nited States Patent Patented Feb. 23, 1960 groups. Moreparticularly, I have found-that the cliern'ical compounds of the general formula:

I wherein R represents an alkyl radical containing from 10 to 22 carbon atoms or an-acyl radical derived from a fatty acid and containing from 10 to 22 carbon atoms,

x and z each represents an integer from 2. to 3, inclusive, and y represents a whole number from 0 to 4,:in-

- clusive, can -be dissolved or dispersed inwell efiluents to inhibit the corrosion of ferrous metals thereby and to impart thereto extreme pressure and other lubricating 1 properties. The well eflluents which have-been so treated In many of the petroleum-producing areas of the arethus especially adapted for use in driving hydraulically operated oil well pumps, but such treatment may of course be employed for its corrosion inhibiting value alone. Thus, the aforementioned compounds-may be advantageously introduced into wells which are free flowing or are equipped with mechanically operated pumps, or

, into well efliuent pipelines, storage tanks, and the like.

ficulties are multiplied when hydraulically operated pumps 3 are employed to raise the well efiluent to the earths surface. Such pumps are positioned near the bottom of the well and, unlike the more familiar well pumps which are mechanically coupled by means of sucker rods to a source of mechanical power at the earths surface, are driven by a hydraulic fluid which is supplied to the pump under pressure via a suitable conduit from a hydraulic pump at the earths surface. A more detailed description of this type of pump and its operation is given at pages 2894 et seq. of the Composite Catalog of Oil Field Equipment and Services, 1957 edition. For obvious reasons it is highly desirable to employ the well eflluent itself as the hydraulic fluid. However, when the well eflluent comprises a high proportion of brine it is entirely unfit for use as a hydraulic fluid. This is due to the aforementioned fact that oil field brines are highly corrosive with respect to the pump parts, and also to the fact that such brines have very little lubricating value and their use causes excessive erosion.

It is accordingly an object of the invention to provide improved means for preventing the corrosion of ferrous metals by oil well efliuents.

Another object is to provide means wherebyoil well efiluents may be employed as hydraulic fluids for driving hydraulically operated oil well pumps.

A further object is to provide means for improving the extreme pressure and lubricity characteristics of oil well efliuents which contain a relatively high proportion of normally corrosive brine, and at the same time inhibit the corrosion-inducing properties of the same.

Other and related objects will be apparent from the following detailed description of the invention, and various advantages not specifically referred to herein will be apparent to those skilled in the art upon employment of the invention in practice.

I have now found that the above objects and attendant advantages may be realized through the provision and use of certain chemical compounds which are thioureas in which each of the carbamyl nitrogen atoms bears a long chain substituent containing amide and/or amine As will-be apparent, the chemical compounds which are employed to accomplish the objects of the invention are either amides or substituted amines depending upon whether R-in the foregoing general formula is an acyl or an alkyl group. The amides are formed by reaction between a long chain monobasic fatty acid and a suitable ethylene or propylene polyamine to form the corresponding mono-amide, andby reaction between the latter and thiourea. These reactions maybe expressed as follows: i

ill 0 wherein R represents an alkyl group and x, y, and 2 have the meanings previously stated;

As examples of suitable acids to be employed in carrying out Reaction 1, above} there may be mentioned lauric, stearic, oleic, ricinoleic, erucic, palmitic, myristic and linoleic acids, as well as mixtures of fatty acids obtained by the hydrolysis of naturally occurring vegetable oils and waxes, e.g. mixed palm oil acids, soya oil acids, rape seed oil -acids,-carnauba wax acids, etc. A preferred fatty acid reactant is the mixture of vegetable oil fatty acids sold under the trade name 0K0 Distillate Acids by Archer Daniel Midlands Co. Said acid mixture has an acid no. ofiabout 16 5 and an average molecular weight of about 300.. Among the polyamines which may be employed in carrying out Reaction 1, there may be mentionedby way of example ethylene diamine, diethylene triamine, triethylene tetramine, tetraethylene pentamine, pentaethylene hexamine, propylene diamine, dipropylene triamine, betaaminoethyl propylamine, tripropylene tetramine, etc. Tetraethylene pentamine is preferred.

While the present class of corrosion inhibiting amides has been described as being formed by two distinct chemical reactions, it is neither necessary nor preferred that the reaction be carried out in two distinct stages. That is, it is not necessary that such compounds be produced by first reacting a fatty acid with an ethylene or propylene polyamine and thereafter, as an additional and separate step, reacting the amino amide so obtained (with or without purification) with thiourea. To the contrary, since the two reactions occur under the same conditions, it is preferred to form the amides simply by heating a mixture of the fatty acid, polyamine and thiourea reactants at a suitable reaction temperature until the reaction is complete as indicated by water and ammonia no longer being evolved from the reaction mixture. The reaction temperature is suitably between about 300 and about 350 F. and the reaction is usually complete in about 6-18 hours. As the reaction equations indicate, two moles each of the fatty acid and polyamide reactants should be employed per mole of the thiourea reactant, although when the reactions are carried out in a single step there is no harm in providing an excess of the acid and polyamine. When the reatcion is carried out in two distinct steps, in the first step it is preferred to employ an excess of the polyamine in order to inhibit the formation of diamides. Upon completion of the reaction, the reaction product may be purified as by distillation, gasstripping, crystallization, etc., to isolate the substituted carbamyl compound in substantially pure form. However, for purposes of the present invention, said compound need not be purified, and in the interests of economy it is preferred to employ the compound in crude form as it occurs in the entire reaction product.

The amine compounds which are included within the foregoing general formula are formed by reacting thiourea with an ethylene o'r propylene polyamine having a long chain alkyl group substituted on one of the primary amine groups. The reaction occurs in accordance with the following equation:

The reaction is carried out at 300-350 F., and its completion is indicated by ammonia no longer being evolved from the reaction mixture. Suitable substituted polyarnine reactants include N-oleyl-ethylene diamine, N-stearyl-triethylene tetramine, N-cetyl-dipropylene triamine, N-lauryl-tetraethylene pentamine, N-heptadecyl-propylene-diamine, N-octadecyl-diethylene triamine, etc.

The following examples will illustrate typical preparations of the present corrosion inhibiting carbamyl compounds, but are not to be construed as limiting the inyention:

Example I 1) A mixture consisting of 150 parts by weight of tetraethylene pentamine and 300 parts by weight of the aforementioned K0 Distillate Acids is heated at 300-320 F. in an open vessel for 8 hours. There is then added 25 parts by Weight of thiourea, and heating is continued at 300 F. for about 6 hours. The product so obtained is a dark-colored viscous liquid consisting essentially of a mixture of compounds of the formula:

Rc'i-I I- c,Hr-NH),-NH

ii i 1 RCN(CzH NH-)4NH (2) A substantially identical product is obtained by heating parts of the polyamine, 300 parts of the 0K0 Distillate Acids and 25 parts of thiourea at 315 F. for about 8 hours.

Example II A mixture of 200 parts by weight of N-oleylethylene diamine and 15 parts by weight of thiourea is heated in an open vessel at 300 F. for 6 hours. The dark viscous liquid product obtained is crude N,N-bis-(beta-oleyl aminoethyl -thiourea:

An equimolecular mixture of lauric acid and dipropylamine triamine is heated at 300 F. for 4 hours, after which there is added one-half mole of thiourea and heating is continued at 320 F. until ammonia is no longer evolved from the reaction mixture. The product so obtained is purified by extraction with alcohol to obtain substantially pure In accordance with one embodiment of the invention, the present class of carbamyl compounds are introduced via the well tubing or casing into a well containing '21 normally corrosive well efiiuent. The amount of carbamyl compound so employed will of course be suificient to effect a substantial degree of corrosion inhibition, which amount will depend upon the nature of the well efiiuent, the temperature and pressure conditions prevailing within the well, and the presence or absence of acidic gases such as carbon dioxide or hydrogen sulfide. Ordinarily, however, the weight of inhibitor maintained in the well will be between about 0.001 and about 0.01 percent of the weight of the fluid in the well. Frequently, it is of considerable convenience to employ the inhibitor in the form of a solution or dispersion in an inert liquid suspending medium which is miscible or 'dispersible'in the well effluent. Suitable liquids of this nature include organic solvents such as benzene, toluene, and light petroleum distillates or extracts, and water or brine. Suitably, such compositions will comprise 10-50 percent of the carbamyl compound and 50-90 percent of the liquid vehicle. Also, if desired, the active ingredient may be employed in conjunction with one or more dispersing or emulsifying agents in order to promote uniform dispersion of the inhibitor in the suspending medium and/or the well fluid. The dispersing agent may be either wateror oil-soluble, or both, and any of the agents conventionally employed in the formulation of corrosio'h'inhibiting compositions may be used, e.g., petroleum sulfonic acids, the Spans and Tweens, fatty acid amides, etc. If desired, a suitable dispersing agent may be formed in situ by preparing one of the amide-type inhibitors employing the fatty acids and alkylene polyamine reactants in excess of the thiourea. The excess fatty acid and polyamine react to form a fatty acid amino amide which is an excellent dispersing agent for the carbamyl compound. T hereaction product so'obtainedthus consists 'of'a'mixaeemsr ture of the corrosion inhibiting carbamyl compound and a dispersing agent for the same. Such type of dispersing agent may also be prepared separately and added to one of the present amide or amine compounds. The present corrosion inhibitors and inhibiting compositions may also be employed in conjunction with scale inhibitors such as the polyphosphates and scale-inhibiting acids.

In accordance with another embodiment of the invention, the present carbamyl compounds and compositions comprising the same are employed as a combined corrosion inhibiting and lubricity agent in well efiluents which are used as the driving fluid for a hydraulically operated well pump. Such pumps are operated in an open circuit, i.e., a portion of the well effluent which is forced from the delivery side of the pump to the earths surface is returned under applied pressure to the power side of the pump and is thence discharged directly into the well. Accordingly, the present inhibitor and lubricity agent may be incorporated into the well eflluent either by introducing it directly into the well as previously explained or by admixing it at the earths surface with that portion of the effluent which is returned to the power side of the pump as the driving fluid. Usuallyit is more convenient and desirable to add the said agent to the efliuent at the earths surface just ahead of the pressure pump, and the amount of agent so added should be suflicient to effect a substantial degree of corrosion inhibition and to increase substantially the lubricity of the well eflluent. Such amount is usually between about 0.001 and about 0.01 percent by weight of the efliuent.

In testing various materials to determine their corrosion inhibiting properties. I have found that test procedures which are carried out at ordinary temperatures and pressures do not reflect accurately the behavoir of the test composition in a well. Thus, inhibitors which appear satisfactory when tested by adding the same to an oil well brine and thereafter contacting the inhibited brine with metal strips at atmospheric temperatures and pressures often prove unsatisfactory when placed in an actual well. Accordingly, I have employed the following rigorous testing method which has been found to simulate actual well conditions to a high degree:

Two 6-inch lengths of steel sucker rod are polished with emery, washed, and accurately weighed. These test specimens are then mounted side-by-side on the head of a 4-liter rocking autoclave. Two hundred ml. of kerosene containing 3-4 drops of the corrosion inhibitor to be tested are then introduced into the autoclave, and the head is bolted on. The autoclave is then purged with carbon dioxide to remove free air. Three and onehalf liters of 3% aqueous sodium chloride from which dissolved air has been removed by purging with carbon dioxide are then introduced into the autoclave, and the latter is pressured up to about p.s.i.g. with carbon dioxide. The simulated well fluid in the autoclave thus contains about 45-60 p.p.m. of the corrosion inhibitor being tested. Kerosene is employed as the hydrocarbon phase of the simulated well fluid since it is not known to contain any of the naturally-occurring corrosion inhibitors which are present in some crudes. The autoclave and contents are heated at l00-110 C. under an autogenous pressure of about 70 p.s.i.g. for 24 hours. Upon completion of the heating period the autoclave is cooled to atmospheric temperature and opened, and the test specimens are removed, washed, and weighed. The efficiency of the inhibitor is calculated as follows:

mi m W1 where W is the loss in specimen weight (total of both specimens) with an uninhibited fluid and W is the loss in specimen weight (total of both specimens) with the inhibited fluid.

The following table sets forth the results obtained when several of the present corrosion inhibitors and com- Inhibiting Test No. Composition Tested Eflicleney,

Percent Product prepared in Example I, part (1);..-" 100.0

Product prepared in Example 1, part 2) 100.0 Product prepared from 25 parts thiourea, parts mixed polyethylene polyamlnes' Polyamlne H") and 300 parts "0K0 Distillate Aci 100. 0

Product prepared in Example ]1 100.0

The extreme pressure and lubricity characteristics of the present class of carbamyl compounds are demon strated by the standard Falex test in which brine taken from a well in Santa 'Fe Springs, California, is employed as the base fluid and the carbamyl compound to be tested is employed in an amount representing about 0.006 percent by weight of the well efliuent sample. The test apparatus is operated for one hour at room temperature, after which the temperature of the brine is determined and the steel test pin is examined visually for scoring. The following table presents the test results obtained by subjecting several of the present carbamyl compounds to the Falex procedure:

While the invention has been described above primarily in terms of the introduction of the present class of corrosion inhibitors into an oil well, either directly or into'a portion of a well effluent which is returned to the well, it should be realized that the principle of the invention is equally applicable to gas wells and to gathering lines, transport lines, storage tanks and any other equipment used in the processing of normally corrosive well eflluents.

Other modes of applying the principle of my invention may be employed instead of those explained, change being made as regards the methods or materials employed provided the compositions or steps stated by any of the following claims, or the equivalent of such stated compositions or steps, be obtained or employed.

1, therefore, particularly point out and distinctly claim as my invention:

1. The method for reducing the corrosiveness of oil and gas well fluids which are normally corrosive with respect to ferrous metals, which method comprises admixing with said fluids a corrosion-inhibiting amount of a substituted thiourea compound having the general formula:

wherein R represents a substituent selected from the class consisting of alkyl radicals containing from 10 to 22 carbon atoms and acyl radicals derived from fatty acids and containing from 10 to 22 carbon atoms, x and 2 each represents an integer from 2 to 3, inclusive, and y represents a whole number from 0 to 4, inclusive.

2. A method as defined by claim 1 wherein the said substituted thiourea compound is employed in the form of a dispersion in an inert liquid suspending medium.

3. A method as defined by claim 1 wherein the said substituted thiourea compound is employed in the form of a dispersion in an inert liquid suspending medium containing sufiicient of an organic dispersing agent to effect dispersion of said substituted thiourea compound in said well fluid.

4. A method as defined by claim 1 wherein, in the given general formula, R represents an acyl group derived from a fatty acid and containing from to 22 carbon atoms.

5. A method as defined by claim 1 wherein, in the given formula, R represents an alkyl group containing from 10 to 22 carbon atoms.

6. A method as defined by claim 1 wherein, in the given formula, x and z each have a value of 2 and y has a value of 4.

7. A method as defined by claim 1 wherein said substituted thiourea is employed in an amount representing between about 0.001 and about 0.01 percent by weight of said well fluid.

8. In the operation of a producing oil well wherein a normally corrosive liquid well efiiuent is pumped from the well to the earths surface by means of a subsurface pump which is driven by an hydraulic fluid supplied thereto from the earths surface under pressure and a portion of said well effiuent is employed as said hydraulic fluid, the improvement which consists in admixing with said portion of well efiluent a corrosion-inhibiting and lubricity-increasing amount of a substituted thiourea cornpound having the general formula:

wherein R represents a substituent selected from the class consisting of alkyl radicals containing from 10 to 22 carbon atoms and acyl radicals derived from fatty acids and containing from 10 to 22 carbon atoms, x and 1 each represents an integer irom 2 to 3, inclusive, and y represents a whole number from 0 to 4, inclusive.

9. A method as defined by claim 8 wherein the said substituted th-iourea compound is employed in the form of a dispersion in an inert liquid suspending medium.

10. A method as defined =by claim 8 wherein the said substituted thiourea compound is employed in the form of a dispersion in an inert liquid suspending medium containing suflicient of an organic dispersing agent to effect dispersion of said substituted thiourea compound in said well fluid.

11. A method as defined by claim 8 wherein, in the given general formula, R represents an acyl group derived from a fatty acid and containing from 10 to 22 carbon atoms.

12. A method as defined by claim 8 wherein, in the given formula, R represents an alkyl group containing from 10 to 22 carbon atoms.

13. A method as defined by claim 8 wherein, in the given formula, x and z each have a value of 2 and y has a value of 4.

14. A method as defined by claim 8 wherein said substituted thiourea is employed in an amount representing between about 0.001 and about 0.01 percent by weight of said well fluid.

References Cited in the file of this patent UNITED STATES PATENTS 2,304,369 Morgan et a1 Dec. 8, 1942 2,598,213 Blair May 27, 1952 2,723,232 Scott Nov. 8, 1955 2,799,648 Nathan July 16, 1957 

8. IN THE OPERATION OF A PRODUCING OIL WELL WHEREIN A NORMALLY CORROSIVE LIQUID WELL EFFLUENT IS PUMPED FROM THE WELL TO THE EARTH''S SURFACE BY MEANS OF A SUBSURFACE PUMP WHICH IS DRIVEN BY AN HYDRAULIC FLUID SUPPLIED THERETO FROM THE EARTH''S SURFACE UNDER PRESSURE AND A PORTION OF SAID WELL EFFLUENT IS EMPLOYED AS SAID HYDRAULIC FLUID, THE IMPROVEMENT WHICH CONSISTS IN ADMIXING WITH SAID PORTION OF WELL EFFLUENT A CORROSION-INHIBITING AND LUBRICITY-INCREASING AMOUNT OF A SUBSTITUTED THIOUREA COMPOUND HAVING THE GENERAL FORMULA 